(a) The present invention concerns the melting and refining of a charge which is continuously introduced at the inlet of a furnace and extracted in refined condition at the bottom thereof, with heat transfer towards at least a substantial portion of said charge by means of wall mounted flame burners directed towards said charge, in which at least part of said flames result from the combustion of an industrial mixture of fuel and oxygen.
(b) Description of Prior Art
In the technique normally used for this type of process, where the furnaces operate continuously, the flames are also produced continuously, with adjustment of the power transferred to the charge, which may be carried out automatically by means of heat probes associated with a power optimizing regulator.
Flames of aero-combustible burners essentially heat by convection and radiation, but it is known that oxy-combustible flames radiate much more than they produce convection. In addition to these two complementary effects, the mechanical effect resulting from the impulse of the flame on the surface of the charge should be noted. Because of the impulse and the inclination of the burner, it is possible to obtain effects which are more or less effective on accumulations, lumps or foams which float at the surface. On the other hand, the aero-combustible flames as well as the oxy-combustible flames produce a certain quantity of polluting gases depending on the concentrations of nitrogen, oxygen and other impurities, and also on the temperature, as well as on the aerodynamic phenomena which are hardly qualifiable but of which the effects are known.
With respect to the particular case of glass production, it is possible to realize that there are one or more burners which maintain the jacket of the furnace at a given temperature and ensure the melting of the material in the furnace, the melting zone occupying 3/4th of the length of the furnace and the refining zone located at the bottom of the furnace generally containing homogeneous liquid glass. In the melting zone, the material is loaded at the inlet of the furnace and floats on a bath of liquid glass. As the compact mass moves into the furnace, it is broken up, melts and falls into pieces to form islands, or lumps, which will slowly move towards the refining zone. It is generally admitted that the quality of glass often depends on a clean and very homogeneous refining zone. The good operation of the process constitutes, however, a hard to reach equilibrium between an appropriate power of the flames, a maximum vault temperature and a clear refining zone. Any deviation would upset the equilibrium and produce an accumulation of lumps in the refining zone, which would cause a degradation of the quality of the glass. For a fixed quality and under a vault temperature near the critical threshold, there corresponds a maximum production which cannot be exceeded under the present conditions without obstructing the refining zone.